This invention relates to a system for reserving the recording of TV programs, and more particularly, to a TV program recording reservation system having a display for displaying items of data required for reserving the recording desired TV programs, and the data about desired TV programs. The invention also relates to a display apparatus for displaying the data about desired TV programs, which can be used in combination with a video tape recorder (VTR) to display the data such that people can easily confirm the desired programs.
A conventional recording/reproduction apparatus such as a VTR has a timer reservation function, by means of which, the data, the recording start and end times, the channel number, and the like, of a program to be reserved are designated, so that the apparatus can be set in an automatic recording state.
With the conventional program reservation systems, the recording of TV programs is reserved by operating keys in accordance with an instruction manual. Data identifying the programs is displayed on a display, such as a phosphor display tube, to confirm whether or not the data correspond to the desired programs. If the display shows the wrong data, the keying operation must be performed again to correct the data. This keying operation is combersome and time-consuming.
Some of the conventional systems of this type can display the data identifying a desired program on the screen of a TV set. The data includes items such as the recording start time, the day of the week, the recording end time, the channel number, and the recording speed. It also includes data showing whether or not the day of the week is within the same week as the day the program is reserved. These data items are displayed in one line or a plurality of lines. When the recording of two or more TV programs is reserved, the items of data about these programs are displayed in the order they have been selected.
With the conventional program reservation systems, only the data regarding the desired programs is displayed on the TV screen, but not the date when the recording of these programs is reserved. Generally, the user wishes to know how many days will pass until the specific program is broadcast, from the day when he or she reserves the program. Since the date of reserving the recording is not displayed on the TV screen, it is difficult for him or her to quickly understand how many days will pass until the specific program is broadcast. The user cannot help but consult the calendar to confirm how many days will pass until the program is broadcast.
A light pen can be used to reserve TV programs. More specifically, the user touches a light pen on the screen of a CRT display, which is a useful man-machine interface, thereby to input data showing the coordinates of the point on the screen the pen is touching. Alternatively, a tablet and a stulus pen can be used to reserve the recording of desired TV programs. In this case, when the stulus pen touches any point on the tablet, the data representing the coordinates of this point can be input. Hence, by using a light pen, or a stylus pen and a tablet, the data identifying a desired TV program can be input, thus reserving the time period for recording the program.
The use of a light pen in reserving the recording of TV programs, however, results in some problems.
The first problem comes from the signal amplifier circuit for receiving a raster beam from the CRT screen and generating a pulse signal for detecting the point on the screen where the light pen is touching.
FIG. 1 shows a conventional signal amplifier circuit used in this type of light pen. Phototransistor 1, as a photodetector attached to a light pen body (not shown), receives a raster beam emitted from the CRT screen. A raster beam signal, obtained by photoelectrically converting the raster beam, is output to amplifier 3 via capacitor 2. Amplifier 3 inverts and amplifies the input raster beam signal, to obtain signal 100 shown in FIG. 2A. Signal 100 is inverted and amplified by amplifier 4 to obtain signal 200, as is shown in FIG. 2B. Signal 200 is input to the positive input terminal (+) of comparator 5. The negative input terminal (-) of comparator 5 receives threshold voltage 300 obtained by voltage-dividing power supply voltage Vcc by resistors 6 and 7. Comparator 5 waveshapes signal 200 with threshold voltage 300, and outputs pulse signal 400 shown in FIG. 2C. A position detector (not shown) has a counter for performing a count operation in synchronism with the raster scan. The count value of the counter is latched in response to the first or last pulse of pulse signal 400, thereby detecting a screen position designated by the light pen.
In the above circut, phototransistor 1 receives a weak raster beam. Alternatively, if phototransistor 1 receives a strong raster beam while the gain of amplifiers 3 and 4 is increased, the light-receiving angle of phototransistor 1 is widened in the vertical direction. In this case, as is shown in FIG. 3, if light pen selection portions a, b, and c are provided adjacent to each other in the vertical direction on the CRT screen, signal 200 and pulse signal 400, shown in FIGS. 4A and 4B, are produced by the circuit shown in FIG. 1. This occurs in spite of light pen selection portion a having been designated by the light pen. More specifically, as is shown in FIG. 4A, signal 200 is formed by the raster beams from light pen selection portions b, a, and c, and accordingly, pulse signal 400 is also formed by light pen selection portions b, a, and c, as is shown in FIG. 4B. Therefore, even though the light pen has designated selection portion a, the position detector erroneously selects selection portion b in response to the first pulse of pulse signal 400, which has been counted and latched, and selects selection portion c in response to the last pulse of pulse signal 400, which has been counted and latched. Therefore, in the conventional light pen signal amplifier circuit, circuit gain is limited, as is also, the amount of light received. Therefore, the conventional circuit can only be used in a specific CRT. When the light-receiving angle is widened in the vertical direction of the light pen, it is also widened in the horizontal direction. However, this horizontal widening of the light-receiving angle be can be cancelled out by the differential effect of the capacitor.
As has been described above, in the conventional light pen signal amplifier circuit, a situation can occur where a weak raster beam is first received and a strong raster beam is subsequently received while the circuit gain is increased. In response, the light-receiving angle of the phototransistor is widened in the vertical direction, and the position where the light pen touches the screen cannot be precisely detected.
The second problem with the use of a light pen in reserving the recording of TV programs, derives from the wave-shaping circuit for shaping the waveform of the signal output from the light pen.
FIG. 5 shows a waveshaping circuit of this type. A signal from photodetector 11 incorporated in a light pen body (not shown) is amplified by amplifier 12, and is supplied to the positive input terminal "+" of comparator 13. The negative input terminal "-" of comparator 13, on the other hand, is supplied with a voltage obtained by voltage-dividing power supply voltage Vcc, as a threshold-level voltage, by voltage-dividing resistors R1 and R2. Comparator 13 waveshapes the output signal from photodetector 11, based on the threshold level. However, the threshold-level voltage applied to the negative input terminal of comparator 13 is obtained by voltage-dividing power supply voltage Vcc. Therefore, the threshold level is influenced by any fluctuation in power supply voltage Vcc. As a countermeasure against any variations in the power supply voltage for each circuit, resistors R1 and R2 must variable resistors, and their resistances must be adjusted to each circuit.
As has been described above, in the conventional waveshaping circuit, the voltage for setting the threshold level of the comparator is influenced by fluctuations and variations in the power supply voltage, and thus, a stable waveshaping operation cannot always be performed.
The third problem with the use of a light pen in reserving TV programs lies with a light pen apparatus used for a TV receiver for displaying a video signal when the horizontal deflection frequency of the signal is converted to twice that of the original video signal.
When a recent-model CRT display such as a TV receiver is connected to a VTR, a video disk player, and the like, a higher image quality is required than would be in the case of displaying a broadcast image. For example, the vertical deflection frequency is left at 60 Hz, and the horizontal deflection frequency is converted to twice that of the conventional interlace scheme, so as to allow display.
This scheme is known as a double scan (noninterlace) scheme. In the conventional 2:1 interlace scheme, since only 262.5 scanning lines are available for each field, an image appears coarse and flickering. In the double scan scheme, since the horizontal deflection frequency is twice that of the conventional interlace scheme, each field has 525 scanning lines. Therefore, flickering is reduced, and a high-quality image is provided.
FIG. 6 is a block diagram showing a conventional circuit using a light pen. In FIG. 6, reference numeral 21 denotes a horizontal counter; and 22, a vertical counter. Horizontal counter 21 counts reference clocks whose frequency is determined in correspondence with pixel size, and generates a horizontal count signal. Vertical counter 22 counts horizontal sync pulses and generates a vertical count signal. The count signals are respectively input to latch circuit 23, and are latched by a signal from light pen 25, which detects a raster beam from screen 26. Therefore, the values of the count signals latched by latch circuit 23 respectively represent horizontal and vertical coordinate data showing the position of light pen 25. A timing signal for various control operations can be generated based on the coordinate data, showing the point where the light pen is touching the screen or the point where the light pen coincides with another predetermined point, so the user can select the operation mode of the recorder.
FIGS. 7A and 7B respectively show a video signal having a horizontal deflection frequency of 15.73426 kHz (NTSC color television scheme) and a video signal whose horizontal deflection frequency is twice that of the above signal, for the sake of comparison. Pointing the light pen to point A, designated in one horizontal period H, in the case of the original horizontal deflection frequency (see FIG. 7A), undesirably corresponds to two points, A1 and A2, in the first and second halves, i.e., 1/2.multidot.H periods when the frequency is doubled, as is shown in FIG. 7B. When the signal shown in FIG. 7B is displayed on a screen, by means of the double scan scheme, point A, shown in FIG. 8A, is converted to points A1 and A2, shown in FIG. 8B.
Therefore, when a point is designated, by the light pen, at the same position as point A for the video signal displayed, as shown in FIG. 8B, the recorder cannot discern whether the control operation has been started in response to pointing the light pen at location A1 or A2.
As has been described above, in the conventional external data input scheme using the light pen, when a video signal, which is converted to have a horizontal deflection frequency twice that of an original video signal, is displayed on a TV receiver performing double scan, i.e., non-interlace scanning, and the light pen is operated, the coordinates of the original video signal on the screen are different from those of the converted video signal on the screen. Therefore, the pointed location of the light pen on the original image cannot be accurately deciphered by the recorder, and an operation error may occur.